Reduced edge instability and improved confinement in the MST reversed-field pinch - art. no. 205001

Improved confinement has been achieved in the MST through control of the po loidal electric field, but it is now known that the improvement has been li mited by bursts of an edge-resonant instability. Through refined poloidal e lectric field control, plus control of the toroidal electric field, we have suppressed these bursts. This has led to a total beta of 15% and a reverse d-field-pinch-record estimated energy confinement time of 10 ms, a tenfold increase over the standard value which for the first time substantially exc eeds the confinement scaling that has characterized most reversed-field-pin ch plasmas.